An introduction to astronomy: designed as a text-book for the use of students in college. By Denison Olmsted ...

bright comet. Astronomers suspectcd thlat its patlh had beei
chaned and that it had been recenltly coInp)elled to move ill
tis Short ellipse, by te disturbing force of Jupiter alid ]his
satellits. French istitute, tlherefore, offered a tliglt
ie for the most complete investigation of thle elements of
this Cometl taking into account anyli circumstances wlhich coiuld
possibly have produced al ateration inll its course. IBy tracing
back its movements for some years prvious to 1770, it was
fouud thatat the bi ing of 1fU7G, it had entered considerably within the sp of piter's atttraction. Calculatilig tile
amot of thisattraction from the known l)roxillity of the two
bodies, its was found what lm t have bCeen its orbit previous to
the time wllen it became sjbcct to thel disturbing actionl of
Jupiter. The result owcd that it thlen moved il an ellipse
of geater extent, having a period of 50( years, and l havi, its
instead o its aphelio n11ear Jupiter. It was therefore evide why, s lon as it continued to circullate in an
obit so fa from the cente of tile system, it was never vis ible
from the earth. In Ja'nuary, Y, Jupiter and tlhe colct
hapned to e very near each otlher, and as both wer'e- moving'
inl the same di1rection, and nearly inl the saine plane, they
remained in the neiohborlhood of each other for several inonthsn
the planet being betwveen the comet and the sunl. Tecon.sequence was,-11 that the comet's orbit was changed iiito a. simaller
ellipse, inl which its revohution was accomp~lishied inl 5. ye~ars.'But ass it wvas lapproaching- the sunl inl 1.779, it h~appened again
to fiall in with Juhpiter. it; was inl thle month of June thfat time
attractionl (.f the planet lbeg-an to have at sensible effect; and it
wats not until thre month of October followving that they wvere
finally separatedl.
At the, time, of tlih Iefir eaest approach, inl Augnust, Julpiter
was, (hstanMt from the coniet onl1y Of its ditnefrom thle
sun, and exerted anl attraction uepont it,2,15) times greater thanl
that of the sun~i. B3y reason of this powverful attraction, Jupiter
being further from the sunl than thec coml-et, thke latter wa's
drawn Out into a niew orbit., which, even at its periheiliomi, camte
no nearer to the sunl than the planet Ceres. Inl this third orbit, thle comret requires about 2.0 years to accopinl~l.s its- revolution;aud bigat so great a. (istance from thle ecarth, it il
invisible, tand wvill. forever remainl so, unl1ess, inl thle courase of